In the Garden | Arbor Day tree and shrub distribution is April 13

Bonnie Orr, master gardener

This is the time of year to plant new trees and to transplant small trees. Learning the problems WSU Master Gardeners answer about landscape trees may help you avoid killing your new tree.

It is an old wives’ tale that the extent of the tree’s root are at the drip line of its branches. In truth, the roots of a mature tree extend outward sometimes one and a half times the tree’s height.

Watering problems are the source of most tree death. Trees lose water through evaporation from the leaves and needles. Depending on the tree’s size and location, the tree can evaporate hundreds of gallons of water on a hot day.

First, overwatering, especially of newly planted trees, drowns the roots the first season, and the tree dies. An even worse problem is when you think you are watering the tree, and you are not. The culprit can be drip irrigation. Drip irrigation is great for xeric perennial and annual flowering plants. It is not an effective way to water trees.

We see three problems with drip irrigation used with young trees and shrubs:

1. Not enough water is delivered with a drip nozzle. If the tree is being drip watered along a line of a variety of plants, by the time the tree has sufficient water, the rest of the landscape plants could easily be swimming.

2. The nozzle is in the wrong place because the tree has grown. When a tree is planted, often the nozzle is placed next to the trunk of the tree or shrub. The tree does not absorb water through the trunk, but constant water on the bark could rot the trunk. More seriously, the roots are a number of feet away from the trunk, and they get no water, so the tree becomes stressed.

3. Clogged nozzles are a clandestine culprit and often cause plant death. When a landscape is created, the drip lines are installed and then landscape cloth is laid down. It is all covered with ornamental bark or gravel. When one bush, such as a burning bush, in a line of shrubs dies, the cause is most likely that the orifice on the dripper is clogged—and there is no way to know this until the plant dies. This system that is supposed to be carefree is problematic because the watering cannot be monitored. As the plant grows, the water is on the stem of the plant and not at the roots.

Humidity and wind are other factors that affect tree health. Our low humidity, less than 30 percent, is a problem for some ornamental trees. We have had a windy spring and summer. The wind, especially on hot days, dehydrates the trees’ leaves. The most frequent damage we see is on dogwood trees. This tree in its native habitat is an understory tree protected from wind and hot sun —and here we most commonly grow it in the center of the lawn.

The second-most common tree problem we see is incorrect planting, specifically planting the tree too deeply. The root flare should not be covered. With all that in mind, plant a tree by removing it from its container or burlap and remove all the soil around the roots. Wash the roots and spread them out flat. The hole you dig will not be as deep as you anticipate but much broader. Do not amend the soil with compost or potting soil. The tree's roots will readily acclimate to your yard’s soil.

There is nothing worse than the wrong tree in the wrong spot. Carefully select the planting site based on the mature size of the tree or shrub. In that way you will not be constantly whacking it back, and it will also not interfere with powerlines, which are 35 feet off the ground.

If you have a wrong tree in the wrong place and wish to transplant it, remember that the roots are not just out to the drip line but many feet further than that. The hole you dig will make an major impact in your landscape — and another wide hole needs to be dug in the new location.

If the tree is over 6 feet tall and the trunk is more than 8 inches around, the transplanting operation may not be a success. You could be better off tearing out the tree and starting over in another place in your yard with another tree.

Plant a tree correctly and enjoy it for years to come. For more tips, contact the WSU Master Gardeners on Mondays and Wednesdays between 1 and 4 p.m. at 667-6540.


A WSU Master Gardeners of Chelan County column appears weekly in The Wenatchee World. Bonnie Orr is one of four columnists featured.